There has been a long-standing demand for a fast operating, reliable and versatile machine whereby articles in the nature of envelopes, single or manifolded sheets, plastic cards or the like can be attached to a web of indefinite length at regular intervals along the web. The tipped-on articles--whatever their character--will hereinafter be designated sheet units. The web serves as a carrier on which the sheet units can be advanced one-by-one through an automatically operating printing device or the like that performs an operation upon each sheet unit. Thus, depending upon the purpose for which the product is intended, the sheet units may be manifolds consisting of two or more sheets with carbon paper between them, to be put through an automatic billing machine; or they may be plastic cards to be processed through a computer-controlled machine that will apply individual identifying indicia to them; or they may be envelopes to be put through an automatic addressing machine. These are but a few examples of a great and steadily increasing variety of such products for which there is a growing demand.
The machine that produces such product must be capable of attaching the sheet units to the web at accurately maintained uniform intervals, and it must be capable of turning out the product at a high rate of speed. For production economy it is also of great importance that the machine be very versatile, since the demand for tipped-on product changes from time to time, and the production machine must be capable of accommodating changes in demand without having to be shut down for each such change to undergo prolonged modification or adjustment.
A machine of the type here under consideration that has enjoyed substantial commercial success is disclosed in Swiss Pat. No. 545,698, which has a counterpart in U.S. Pat. No. 3,871,639. In that machine the sheet units move in one direction while the endless web moves in the opposite direction until the sheet units and the web reach a location at which they are brought together and adhesively connected. Fixed stops provide for the positioning of the sheet units relative to the endless web. From the location at which the adhesive connection takes place, the web with the attached sheet units moves on in an orderly manner.
Because of the movement in opposite directions of the sheet units and the endless web, the web must be brought to a stop for each sheet unit that is to be connected to it, with the result that production capacity is limited, and therefore this disclosed method and apparatus is unsatisfactory for many conditions.
U.S. Pat. No. 3,540,970 discloses a machine for tipping individual sheets together in pairs or multiples. The machine of this patent is capable of being operated only with individual sheet units that are attached directly to one another. It cannot be employed for attachment of individual sheets or slips to an endless web at spaced apart locations along it.
U.S. Pat. No. 3,249,352 discloses a machine for attaching tab cards to a web of indefinite length. The tab cards had to have perforations along their side edges and the web stock had to be similarly perforated because the perforations were relied upon to establish the cards at the desired locations along the web. The machine was not well adapted for producing other types of product than the one for which it was specifically intended, and it was confined to use with tab cards having dimensions defined by the spacing of the perforations.
U.S. Pat. No. 3,879,028 discloses a more versatile machine, but, again, one that could only operate with sheet units having perforations at fixed spaced intervals and with a web having perforations at the same intervals. The perforation intervals fixed the size increments of the sheet units that could be handled by the machine and imposed a severe limitation upon the variety of products that it could produce.
U.S. Pat. No. 3,200,719 discloses a machine for attaching envelopes to a continuous web. It was intended to operate with imperforate envelopes and an imperforate web, so that in theory it seemed to be capable of tipping sheet units to a web at any desired spacing intervals, rather than being confined to spacing increments fixed by predetermined perforation intervals. Furthermore, it was arranged for continuous travel of its web rather than for intermittent web travel, and in that respect it seemed to promise high production speeds. In fact, however, the machine was not very versatile, and it tended to be slightly inaccurate in its spacing of sheet units along the web. It had a distributing conveyor mechanism by which the sheet units were brought into properly spaced relationship to one another while moving forward towards union with the web; but that mechanism was not capable of arranging the sheet units in overlapping relationship, and therefore the machine could not produce a type of product for which there is a substantial demand. Another deficiency of the machine was more subtle and may not have been apparent in all applications. After the envelopes had been brought into properly spaced relation to one another on the distributing conveyor mechanism, they were fed from that mechanism to a system of roller conveyors by which they were transported to their union with the web. In passing from the distributing conveyor mechanism to the roller conveyor system the envelopes had to be accelerated in their forward edgewise motion. Such acceleration could not take place instantaneously, and therefore there was always a slight slippage between each envelope and rollers of the roller conveyor system. With very uniform envelopes and careful adjustment, that slippage could be the same for every envelope, but any variation in the rate of acceleration from envelope to envelope resulted in irregular spacing of envelopes along the web. Thus the machine was obviously not well adapted for operation with different types of sheet units.
From the foregoing discussion it can be seen that a basic problem in this art has been that of preliminarily establishing sheet units in the spaced relationship that they are intended to have when attached to the web and then maintaining them in that relationship all the way to their union with the web. Any of several known expedients can be employed for bringing sheet units into a desired relationship to one another, whether at slightly spaced intervals, or in edge-to-edge contiguity, or with a predetermined overlap. However, the sheet units cannot be united with a web while they are being carried by any of the known arranging mechanisms, and therefore--especially in a high-production machine wherein the web remains in continuous motion--the sheet units must be transferred from the arranging mechanism to some other device by which their union with the web is brought about.
Various arrangements have been proposed whereby the arranged sheet units and the web are brought together while they are traveling along a curved path defined by a rotating drum or the like. Although apparently satisfactory for many types of product, such arrangements cannot operate satisfactorily with sheet units in the form of relatively thick manifolds, owing to the difference in radius as between the innermost and the outermost sheets of the manifold as it moves around the curved path.
Desirably, therefore, the sheet units should move edgewise in a straight path, not only while they are advancing towards the zone at which they are united with the web but also as they move through that zone, and preferably through some further substantial distance beyond that zone. Furthermore, once the sheet units have been brought into the desired relationship to one another, they should continue their edgewise forward motion at a steady rate, equal to the forward speed of the web, without being accelerated or decelerated in such motion.
In general, what has heretofore been lacking in the art, but has manifestly been needed, is apparatus for applying labels, sheets, slips or the like to an endless web at locations thereon that are spaced apart by predetermined distances, and for causing the individual sheet units to be bonded to the web at those locations, and whereby those operations are accurately performed at very high speed to thus afford a high rate of production.
The general object of the present invention is to satisfy this want.